Several GIS platforms now offer apps that synchronise GIS-based fieldwork between your computer and your phone or tablet. With options to add differential GPS equipment to your mobile GIS kit and the capacity to take your basemaps and other data with you into the field, mobile-GIS eliminates the disconnect between data capture and GIS. So how do the latest mobile-GIS apps measure up in the field? Here I review two that I tested recently during fieldwork at the classical site of Olynthos, during ongoing fieldwork in Greece.
There have long been efforts to replace large and complex survey kit with smaller handheld devices. Until recently these typically involved either a substantial cost for the procurement of specialist hardware and software (such as the Leica Zeno and ESRI ArcPad) or experience in the management (and often programming) of open-source data solutions (such as many described in this discussion in GIS Stack Exchange). If you didn’t have the financial or programming resources to use these, then you were stuck with combining survey equipment, like total stations or differential GPS (see image left) with several different software programmes in order to create, process and import your data in a GIS (Geographic Information System). Once fieldwork data was incorporated into the GIS, it often required further processing to produce GIS-friendly layers for analysis and presentation and if the data was collected by a non-GIS specialist there were many opportunities for misunderstandings about the format required for GIS compatibility, resulting in stress and additional delay for one or both parties.
The advent of mobile phone and tablet compatible mobile-GIS apps has opened a range of new possibilities for recording fieldwork directly in a mobile-GIS platform, synced to your online or desktop GIS. During recent fieldwork at the site of Olynthos, Greece I trialed two different mobile-GIS apps ArcGIS Collector and QGIS QField on my Samsung Galaxy tab S2, running Android 7.
The Olynthos Project is an interdisciplinary research project in northern Greece directed by Lisa Nevett of the University of Michigan, Zosia Archibald of the University of Liverpool and Bettina Tsigarida of the Ephorate of Pella. The project combines the excavation of houses on the north and south hills of the classical town, with field surface survey of the surrounding countryside and various scientific analyses (Nevett et al. Forthcoming). The project has typically used total stations for recording on site and printouts of Google Earth for identifying surveyed fields, with data from both sources incorporated into the project GIS in subsequent stages. Tablet-based mobile-GIS survey is not appropriate for precise recording of archaeological features in the excavation trenches, as GPS units integrated into tablet computers are only precise to c. 2.5-5m. But once combined with a satellite image basemap, this level of precision is perfectly acceptable for recording surveyed fields in the surrounding countryside or surface collection in grid squares on the unexcavated parts of the site.
The Olynthos Project began using ArcGIS Collector for surface survey following initial development of the Olynthos Project ArcGIS Online group and ArcGIS Collector maps by Peter Knoop and Caitlin Dickinson of the University of Michigan. The recent field season in July 2017 gave me the opportunity to test ArcGIS Collector against QGIS QField during archaeological fieldwork.
ArcGIS Collector and QGIS QField are essentially simplified versions of their big brother desktop GISs, optimised for field data collection on a small mobile device with limited connectivity and processing power. Both apps operate on similar principles. You produce layers in your desktop GIS, convert them and upload them (directly or via the web) to your mobile device. The Collector and QField apps then run these ‘mobile’ versions of your GIS projects enabling you to a view, and create GIS layers in a format that is suitable for smaller screens and simpler for mobile devices to process. Both apps are designed for creating data in the field using the device’s GPS or a separate unit compatible with it. Both raster and vector data are supported and require processing for inclusion in the mobile app, raster data usually requires tiling to ensure it displays efficiently.
Despite their many similarities there are several significant differences between ArcGIS Collector and QGIS QField, not least of which is that Collector is proprietary and requires you (or your organisation) to have an online subscription, while QField is free and opensource (like all QGIS products).
Since many archaeologists, archaeological units and universities already have ArcGIS licenses and online subscriptions ArcGIS Collector is likely to be a significant player in future mobile-GIS for archaeological fieldwork. It requires you to have an ArcGIS Online account, through which the uploading and downloading or your mobile GIS data is managed. Setting up your Collector app is therefore a staged process, first you must share the layers you want to use to your ArcGIS Online account. Then create a map in your online account with a basemap (either ERSI ArcGIS imagery or your own tiled raster) and the layers you want to see or edit in the field. Finally you download that map to your Collector app on your mobile device. This process is a little cumbersome and confusing, particularly for those who haven’t used ArcGIS Online before. It’s easy to upload a layer but then fail to share or publish it correctly for you or others to view or edit it in Collector. This can be irritating, but there are online help pages and the usual forums (such as the ever-brilliant GIS stack exchange) and once you’ve created one map for Collector, familiarity makes the process a lot easier.
The good news is that once you’ve grasped the online part of the process, the interface (above) is clean and easy to use and using the app in the field is incredibly simple and straightforward. Once the app is linked to your ArcGIS Online account it identifies all the maps you and others in your organisation/group have created and offers you the opportunity to collect data using them.
You can operate Collector in two modes. If you just click on a map in Collector, it loads the map directly from your ArcGIS Online account via wifi or mobile data. This is straightforward, but if you don’t want to use mobile data or the connection is slow, then it’s a pain. Alternatively you can click ‘download’ on the map and download a section of it to Collector for offline editing. With a downloaded map you can use a basemap from your ArcGIS Online account, from ESRI ArcGIS imagery or from a raster on your device. You pick the geographical area you’re working in and the level of detail you need for your fieldwork and Collector will download just that area of your AcrGIS Online map so you can work offline, saving you time and mobile data. Once you finish recording in the field you can sync your downloaded map, uploading all your edits to their respective layers in ArcGIS Online (if you use Collector without downloading, the syncing occurs in real time via wifi or mobile data). You then return the edits to your computer by opening ArcGIS Online in your desktop GIS and adding your edited layers. The process within the app is generally slick and comfortable but a major issue with Collector is that it doesn’t currently support snapping. This necessitates various topological checks and editing of your data in ArcGIS desktop after you’ve downloaded it. I found this to be a serious deficiency in the ArcGIS Collector format, which is all the more surprising given that Collector is substantially older than QField, where snapping is straightforward to set up.
Overall I found Collector a straightforward app to use. Although the need to run the data through ArcGIS Online is slightly irritating and predisposes the process to additional errors, this is typical of a platform which is trying to serve a great variety of purposes across many industries. The Collector app isn’t perfect (the absence of snapping is a serious defect in my opinion) and crashed a couple of times, but performance definitely improved when I downloaded the maps instead of using them through mobile-data/wifi. For anyone using Collector I would recommend keeping the number of layers, particularly raster layers, to a minimum by only using the layers you absolutely need in any given map. You can also improve performance by turning your rasters into tile packages and transferring them directly from your desktop to your mobile device. When you download your map to the Collector app it is also advisable to limit the ‘Work Area’ that is downloaded to the minimum that is necessary to complete your fieldwork, as this will speed up the download and performance generally.
QField is the opensource QGIS version of ArcGIS Collector. It’s relatively new and still in the experimental stage, so may have some bugs, although these will be worked out as researchers find and report them. One great advantage of QField is that all data preparation takes place on your desktop GIS and there is no need to upload anything to an online account. Instead you prepare your data in QGIS desktop (including symbology, snapping and attribute fields), package it for QField using the QFieldSync plugin (Note that you must be using QGIS 2.18 for the QFieldSync plugin to function correctly) and then physically transfer it to your mobile device (with a cable). This eliminates many of the irritations of the ArcGIS Online transfer process, but does mean you need to pay attention to the QField online documentation about where you should store your project folder on your mobile device (I found this stage a little confusing, but more information will undoubtedly come out as people use QField more).
On first look QField appears a little more confusing than ArcGIS Collector and the interface (see image above) is a little clunkier, but these are minor issues and will undoubtedly be resolved as development continues. Like ArcGIS Collector QField allows you to browse and view existing layers and create features. The workflows are typically clean and efficient, but unlike ArcGIS Collector you cannot edit the geometries of features that were transferred into QField from your desktop. You can only create and edit the geometry of new features. Although you can edit the attributes of existing features in QField, it is slightly disappointing that you cannot edit their geometries as it limits your capacity to edit previously created archaeological features based on new data obtained during your fieldwork. It’s not an insurmountable problem, but it is irritating. Hopefully this will change with further development.
There are a couple of other minor issues with QField functionality. It’s frustrating that you cannot view features created outside of QField in vector layers set to ‘offline editing’. The advent of Android 7 has resulted in a bug in photo capture in the app (https://github.com/opengisch/QField/issues/133), which is currently being resolved but prevented me from taking photos in the app. However QField is still in the experimental testing phase and will undoubtedly improve with development. Given its stage development the quality of QField bodes well for the future of opensource mobile-GIS.
GPS and accuracy
As our current survey fieldwork does not require better accuracy than the c. 2.5-5m provided by the onboard GPS I haven’t attempted to use these apps with an external GPS device. If necessary it would be possible to improve the accuracy with any one of a number of additional GPS devices, as described in this blog. This would undoubtedly add to the amount of equipment (and expense) involved and might provoke more compatibility and processing issues to occur, but would permit mobile-GIS to be used for much more detailed recording.
The future of mobile-GIS?
ArcGIS Collector and QGIS QField are very similar mobile-GIS apps and both permit a user to record data easily in the field, to a modest level of precision, and sync that data with their existing GIS using just a tablet or smartphone. Both apps significantly sped up data collection in the field and eliminated the need for additional data entry as records were transferred from total station or paper records to the desktop GIS. Currently ArcGIS Collector is the more developed and flexible platform, provided you can get access to it and are prepared to put up with the irritation of processing everything through ArcGIS Online. But QGIS QField is catching up fast, and has already surpassed Collector in some areas (notably the presence and ease of snapping) despite its experimental status. Although the occasional bugs might put some off QField, if you don’t have the resources for ArcGIS Collector, already have some familiarity with QGIS and are prepared to work around the occasional issue, QField is a great little platform that will only get better. In a few years’ time I can easily imagine using QField for preference if it continues to develop along its current lines.
I am grateful to the Peter Knoop and Caitlin Dickinson of the University of Michigan for creating the Olynthos ArcGIS Online account and initial ArcGIS Collector maps of the site. I am also grateful to the University of Michigan for access to the Olynthos field data, ArcGIS Online and opportunity to work with the Olynthos Project. I am particularly grateful to Zosia Archibald for suggesting my involvement in the project, to David Stone and Lisa Nevett for collaboration on the GIS, to Bettina Tsigarida of the Ephorate of Pella and to the Hellenic Ministry of Culture and Sports for permission to investigate the site and their collaboration on the project.
For more information about the Olynthos Project see the Project website.
For fieldwork results to date see the forthcoming interim report Lisa C. Nevett, E. Bettina Tsigarida, Zosia H. Archibald, David L. Stone, Timothy J. Horsley, Bradley A. Ault, Anna Panti, Kathleen M. Lynch, Hannah Pethen, Susan M. Stallibrass, Elina Salminen, Sean Taylor, John Manousakis and Dimitrios Zekkos. Forthcoming. The Olynthos Project: Interim Report on the first three years of fieldwork (2014-2016). Annual of the British School at Athens.